Method of manufacturing non-aqueous secondary battery

ABSTRACT

A method of manufacturing a non-aqueous secondary battery includes the steps of preparing a case main body, preparing a lid, applying a lubricant to a contact location, and assembling a lid to an open end of the case main body. In the step of preparing a lid, a lid to be fitted to the open end of the case main body is prepared. In the step of applying a lubricant, the lubricant is applied to at least a portion of the contact location at which the case main body and the lid are in contact with each other. In the step of assembling the lid to the open end, the lid is assembled to the open end with the lubricant having been applied to the contact location. The lubricant may be a solvent used in a non-aqueous electrolyte solution for non-aqueous secondary batteries.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese Patent ApplicationNo. 2018-160068 filed on Aug. 29, 2018, which is incorporated byreference herein in its entirety.

BACKGROUND

The present disclosure relates to a method of manufacturing anon-aqueous secondary battery.

JP 2015-060831 A discloses a non-aqueous electrolyte secondary battery.The publication discloses that an electrode assembly is enclosed insidea case main body through an open end of the case main body, a lid isfitted to the open end, and the fitted portion between the lid and thecase main body is laser welded all around.

JP 2016-2562 A discloses preparing what is called a prismatic case mainbody in a flat rectangular parallelepiped shape and a plate-shaped lidto be fitted to an open end of the case main body, the open end beingone side end of the case main body that is open, fitting the lid to theopen end of the case main body, and laser-welding the lid and the openend of the case main body all around along the peripheral edge of theopen end.

SUMMARY

A non-aqueous secondary battery is typically furnished with a lid and acase main body provided with an open end. The lid and the open end ofthe case main body are laser welded together all around so that the openend of the case main body is hermetically sealed. Although assembling ofthe lid and the case main body requires high precision in shapes anddimensions of parts, it is possible that an overlapping portion may formbetween the lid and the open end of the case main body due to thetolerance in dimensions of the parts. This means that the lid and thecase main body may rub against each other when fitting the lid to theopen end of the case main body.

A method of manufacturing a non-aqueous secondary battery disclosedherein includes the steps of preparing a case main body, preparing alid, applying a lubricant to contact locations, and assembling a lid toan open end of the case main body.

In the step of preparing a case main body, the case main body isprepared. The case main body prepared in this step includes an enclosingspace for enclosing an electrode assembly and an open end for insertingthe electrode assembly into the enclosing space.

In the step of preparing a lid, the lid to be fitted to the open end ofthe case main body is prepared.

In the step of applying a lubricant, the lubricant is applied to atleast a portion of the contact locations at which the case main body andthe lid are in contact with each other.

In the step of assembling a lid to an open end, the lid is assembled tothe open end with the lubricant having been applied to the contactlocations. The lubricant may be a solvent used in a non-aqueouselectrolyte solution for non-aqueous secondary batteries.

The just-described method of manufacturing a non-aqueous secondarybattery reduces the friction that is produced when assembling the lid tothe open end and accordingly reduces the formation of contaminants.

Here, in the step of applying a lubricant, the lubricant may be appliedto at least one of the case main body and the lid.

In addition, the open end of the case main body may include a pluralityof linear portions and a plurality of curved portions arranged along anedge of the open end, and each of the contact locations may include aplurality of linear portions and a plurality of curved portions arrangedalong the edge of the open end. In this case, it is possible that in thestep of applying a lubricant, the lubricant may be applied to at leastthe plurality of curved portions of the contact locations.

It is also possible that the open end of the case main body may be in asubstantially rectangular shape and may include a step along an innerside wall of the case main body. In this case, the lid may be asubstantially rectangular-shaped plate material fitted to the open end.It is possible that in the step of applying a lubricant, the lubricantmay be applied to at least one of corner portions of the substantiallyrectangular-shaped open end and corner portions of the lid.

In addition, the lubricant may be at least one solvent selected from thegroup consisting of cyclic carbonate solvents, chain carbonate solvents,and ether solvents.

For example, the lubricant may be at least one solvent selected from thegroup consisting of ethyl methyl carbonate, ethylene carbonate, dimethylether, diethyl carbonate, propylene carbonate, and dimethyl carbonate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view for schematically illustrating process stepsof a method of manufacturing a non-aqueous secondary battery.

FIG. 2 is a schematic view for schematically illustrating process stepsof the method of manufacturing a non-aqueous secondary battery.

FIG. 3 is a plan view illustrating an open end 41 b of a case main body41.

FIG. 4 is a plan view illustrating the open end 41 b of the case mainbody 41 to which a lid 42 is fitted.

DETAILED DESCRIPTION

Hereinbelow, embodiments of a method of manufacturing a non-aqueoussecondary battery according to the present disclosure will be describedin detail. It should be noted, however, that the embodiments describedherein are, of course, not intended to limit the present invention. Thepresent invention is not limited to the embodiments described hereinunless specifically stated otherwise.

FIGS. 1 and 2 are schematic views for schematically illustrate themanufacturing steps of the method of manufacturing a non-aqueoussecondary battery disclosed herein.

The method of manufacturing a non-aqueous secondary battery disclosedherein includes the steps of preparing a case main body 41 (see FIGS. 1and 2), preparing a lid 42 (see FIGS. 1 and 2), applying a lubricant(not shown), and assembling the lid 42 to an open end 41 b.

In the step of preparing the case main body 41, the case main body 41 isprepared. As illustrated in FIGS. 1 and 2, the case main body 41prepared in this step may include an enclosing space 41 a for enclosingan electrode assembly 20 and an open end 41 b for inserting theelectrode assembly 20 into the enclosing space 41 a. In the step ofpreparing the lid 42, the lid 42 to be fitted to the open end 41 b isprepared.

The shape of the case main body 41 and the shape of the lid 42 are notlimited to a particular shape unless specifically stated otherwise. Inthe embodiment shown in FIGS. 1 and 2, the case main body 41 may be whatis called a prismatic aluminum case, for example, in a flatsubstantially rectangular parallelepiped shape. The case main body 41has the enclosing space 41 a that can enclose the electrode assembly 20that is formed in a flat shape.

One of the flat surfaces of the case main body 41 is open. In thisembodiment, an open end is formed in one side face of the case main body41 that is perpendicular to one of the longer sides of a widerectangular face with the widest area among its rectangular faces. Thisopen end serves as the open end 41 b for enclosing the electrodeassembly 20 into the enclosing space 41 a. FIG. 3 is a plan viewillustrating an open end 41 b of a case main body 41. In thisembodiment, a stepped portion 41 b 1 is provided at an inner side faceedge of the open end 41 b of the case main body 41. The lid 42 (seeFIGS. 1 and 2) is fitted to the stepped portion 41 b 1. FIG. 4 is a planview illustrating the open end 41 b of the case main body 41 to which alid 42 is fitted. This embodiment shows that the stepped portion 41 b 1is provided at the entire perimeter of the open end 41 b of the casemain body 41, but this is merely an example. The stepped portion 41 b 1may not be provided throughout the entire perimeter of the open end 41 bof the case main body 41. The stepped portion 41 b 1 may be provided ina portion of the perimeter of the open end 41 b of the case main body41. For example, it is possible that the stepped portion 41 b 1 may beprovided only along the shorter sides of the open end 41 b of the casemain body 41.

The electrode assembly 20 is what is called a battery element. Thespecific embodiment of the electrode assembly 20 is not limited to theembodiments illustrated herein, unless specifically stated otherwise.Although not shown in detail in the drawings, the electrode assembly 20illustrated herein may be what is called a stacked electrode assembly,in which positive electrode sheets and negative electrode sheets arealternately stacked with separator sheets interposed therebetween. Inanother embodiment of the electrode assembly 20, it is possible that theelectrode assembly may include a positive electrode sheet, a firstseparator sheet, a negative electrode sheet, and a second separatorsheet, each of which may be a long strip-shaped member. The electrodeassembly 20 may be what is called a wound electrode assembly in whichthe positive electrode sheet and the negative electrode sheet, eachbeing a long strip-shaped member, are alternately stacked and wound withthe first separator sheet and the second separator sheet interposedtherebetween.

The positive electrode sheet may include a positive electrode currentcollector foil (for example, an aluminum foil), a positive electrodeactive material layer containing a positive electrode active material,and an uncoated portion defined with a constant width along one lateraledge of the positive electrode current collector foil. The positiveelectrode active material layer may be formed on both faces of thepositive electrode current collector foil, except for the uncoatedportion. The uncoated portion of the positive electrode currentcollector foil, on which the positive electrode active material layer isnot formed, may serve as a positive-electrode current collecting portion20 a of the electrode assembly 20. In a lithium-ion secondary battery,the positive electrode active material is a material that releaseslithium ions during charge and absorbs lithium ions during discharge,such as lithium-transition metal composite material. Generally, otherthan the lithium-transition metal composite material, various materialshave been proposed for use as the positive electrode active material,and the positive electrode active material is not limited to aparticular material.

The negative electrode sheet may include a negative electrode currentcollector foil (for example, a copper foil), a negative electrode activematerial layer containing a negative electrode active material, and anuncoated portion defined with a constant width along one lateral edge ofthe negative electrode current collector foil. The negative electrodeactive material layer is formed on both faces of the negative electrodecurrent collector foil, except for the uncoated portion. The uncoatedportion of the negative electrode current collector foil, on which thenegative electrode active material layer is not formed, may serve as anegative-electrode current collecting portion 20 b of the electrodeassembly 20. In a lithium-ion secondary battery, for example, thenegative electrode active material is a material that absorbs lithiumions during charge and releases the absorbed lithium ions duringdischarge, such as graphite. Generally, other than graphite, variousmaterials have been proposed for use as the negative electrode activematerial, and the negative electrode active material is not limited to aparticular material.

The separator sheet may be formed of, for example, anelectrolyte-permeable porous resin sheet that achieves desired heatresistance. Various proposals have been made about the separator sheet,and there is no particular restriction on the separator sheet. It may bepossible that the negative electrode active material layer of thenegative electrode sheet cover the positive electrode active materiallayer of the positive electrode sheet with the separator sheetinterposed between the negative electrode active material layer and thepositive electrode active material layer. It may also be possible thatthe separator sheet cover the positive electrode active material layerof the positive electrode sheet and the negative electrode activematerial layer of the negative electrode sheet.

In the embodiment shown in FIGS. 1 and 2, the electrode assembly 20 is awound electrode assembly, which is in a substantially rectangular flatshape such that it can be enclosed in the enclosing space 41 a of thecase main body 41. In this case, the uncoated portion serving as thepositive-electrode current collecting portion 20 a and the uncoatedportion as the negative-electrode current collecting portion 20 b areoriented so as to protrude laterally in opposite directions (i.e., alongthe longer sides). The uncoated portion serving as thepositive-electrode current collecting portion 20 a protrudes from one ofthe lateral edges of the separator sheet 23. The uncoated portionserving as the negative-electrode current collecting portion 20 bprotrudes from the other one of the lateral edges of the separator sheet23.

The lid 42 is fitted to the open end 41 b of the case main body 41. Inthis embodiment, the stepped portion 41 b 1 is provided at the edge ofthe open end 41 b of the case main body 41 that faces inward. The lid 42is a plate-shaped member that can be fitted with the stepped portion 41b 1. In addition, in the embodiment, a positive electrode terminal 31and a negative electrode terminal 32 are attached to the lid 42. Thepositive electrode terminal 31 and the negative electrode terminal 32are provided with current collector pieces 31 a and 32 a, respectively,such as to extend into the case main body 41. The positive-electrodecurrent collecting portion 20 a of the electrode assembly 20 is attachedto the current collector piece 31 a of the positive electrode terminal31 by, for example, welding. The negative-electrode current collectingportion 20 b of the electrode assembly 20 is attached to the currentcollector piece 32 a of the negative electrode terminal 32. Asillustrated in FIG. 4, the lid 42 is provided with a filling port 42 dand a safety vent 42 e. When assembling the lid 42 to the case main body41, the filling port 42 d is open. The lid 42 is assembled to the casemain body 41, then the lid 42 is welded to the case main body 41, and anelectrolyte solution is filled into the case main body 41. Thereafter,the filling port 42 d is sealed.

In this embodiment, as illustrated in FIGS. 1 and 2, the lid 42 isfitted to the case main body 41 while the electrode assembly 20 isplaced into the case main body 41 with the electrode assembly 20attached to the lid 42. At this time, as illustrated in FIG. 1, forexample, the electrode assembly 20 attached to the lid 42 is orientedupward, and the open end 41 b of the case main body 41 is orienteddownward and arranged above the electrode assembly 20. Subsequently, asillustrated in FIG. 2, the lid 42 is moved upward relative to the casemain body 41, so that the electrode assembly 20 is placed into the casemain body 41 through the open end 41 b. Then, the electrode assembly 20is enclosed in the enclosing space 41 a, and the lid 42 is fitted to thestepped portion 41 b 1 of the open end 41 b. It should be noted that theorientation of the electrode assembly 20 when enclosed in the enclosingspace 41 a, for example, is not limited to the example shown in thedrawings. Moreover, in the process as described above, the case mainbody 41 and the lid 42 may be supported by appropriate tools, forexample, and appropriate position alignment may be carried out with, forexample, robot arms of an automatic assembly robot when fitting the casemain body 41 and the lid 42 to each other. Thus, because the lid 42 isfitted to the open end 41 b of the case main body 41 from below in thisway, contaminants, if produced during fitting of the lid 42, areunlikely to enter the inside of the case main body 41.

The lid 42 is formed of the same type of aluminum material as the casemain body 41. The lid 42 is fitted into the stepped portion 41 b 1 ofthe case main body 41 and welded thereto by laser welding. In this case,the lid 42 and the case main body 41 are welded to each other so that nogap exists therebetween. The shape of the stepped portion 41 b 1 of thecase main body 41 and the shape of the lid 42 are formed so as to have anarrow gap therebetween so that the gap between the lid 42 and the casemain body 41 can be closed by laser welding. Even so, the case main body41 and the lid 42 may rub against each other within the range ofdimensional tolerance, when fitting the lid 42 to the case main body 41.

For example, a peripheral edge portion 42 a of the lid 42 may rubagainst an inner side wall 41 b 2 (see FIG. 3) of the open end 41 b ofthe case main body 41. The open end 41 b in such a substantiallyrectangular shape shows high rigidity in regions surrounding cornerportions 41 c of the open end 41 b. Therefore, the side wall 41 b 2 ofthe open end 41 b and the peripheral edge portion 42 a of the lid 42 areprone to rubbing against each other at the corner portions 41 c and inthe regions surrounding the corner portions 41 c of the open end 41 b.

In the step of applying a lubricant, the lubricant (not shown) isapplied to a contact location at which the case main body 41 and the lid42 are in contact with each other when fitting the lid 42 to the openend 41 b of the case main body 41.

The contact location may vary depending on the shapes of the case mainbody 41 and the lid 42. In the embodiment shown in FIGS. 1 and 2, thecontact location includes the side wall 41 b 2 and the stepped portion41 b 1 of the open end 41 b of the case main body 41, and the peripheraledge portion 42 a of the lid 42.

Herein, the lubricant may be a solvent that is commonly used in anon-aqueous electrolyte solution for non-aqueous secondary batteries.The solvent used in a non-aqueous electrolyte solution for non-aqueoussecondary batteries may be an organic solvent that has a requiredvoltage tolerance. The required voltage may be determined from thevoltage that is produced in charging and discharging of the non-aqueoussecondary battery. When the lubricant is a solvent used in a non-aqueouselectrolyte solution for non-aqueous secondary batteries, it is unlikelyto cause a problem even when the lubricant remains inside the batterycase. It should be noted that the solvent used in a non-aqueouselectrolyte solution for non-aqueous secondary batteries is not limitedto the solvent used in the non-aqueous electrolyte solution of thenon-aqueous secondary battery manufactured according to the presentdisclosure.

An example of the solvent used in a non-aqueous electrolyte solution fornon-aqueous secondary batteries is a solvent containing at least onematerial selected from cyclic carbonate solvents, chain carbonatesolvents, and ether solvents. Specifically, it is possible to use asolvent containing at least one material selected from ethyl methylcarbonate, ethylene carbonate, dimethyl ether, diethyl carbonate,propylene carbonate, and dimethyl carbonate. These examples of thematerials specifically mentioned herein may be used either alone or incombination as appropriate. Because these materials show highvolatility, these materials volatilize in later processing steps.Moreover, because these materials are used in a non-aqueous electrolytesolution for non-aqueous secondary batteries, there will be noparticular adverse effect on the later processing steps even if thelubricant does not volatilize but remains in the battery case.Furthermore, the materials listed here have little adverse effects onthe battery performance even if the material remains inside the cellafter having been used as the lubricant as described above. Also, thematerials listed here will not affect the welded portion even if thematerial adheres onto the welded portion.

Examples of materials that are unsuitable as the lubricant includematerials such as press forming oil and grease. Such materials containchlorine or sulfur, and may react with aluminum, which is used for thecase main body 41 and the lid 42. Materials that can corrode the casemain body 41 and the lid 42 and materials that do not volatilize easilyare also unsuitable. Materials that do not vaporize easily are likely toremain inside the cell. In addition, materials that do not vaporizeeasily may cause adverse effects when welding the case main body 41 andthe lid 42 together. Therefore, such materials are unsuitable for thelubricant.

In the step of assembling the lid 42 to the open end 41 b, the lid 42 isassembled to the open end 41 b with the lubricant having been applied tothe contact location. At this time, because the lubricant is applied tothe contact location between the open end 41 b and the lid 42, frictiontherebetween is reduced when the lid 42 is fitted to the open end 41 b.In this case, the locations at which the lid 42 and the open end 41 bare fitted may overlap each other even within the tolerance in geometricdimensions, for example. This causes the lid 42 and the open end 41 b torub against each other. According to the manufacturing method disclosedherein, the lubricant is applied to the contact location between theopen end 41 b and the lid 42. Therefore, even if the lid 42 and the openend 41 b rub against each other, they are unlikely to producemicroscopic contaminants. In addition, the lubricant applied to thecontact location where the lid 42 and the open end 41 b are in contactwith each other is forced out of the contact location when fitting thelid 42 to the open end 41 b. As a result, even if contaminants areproduced by the lid 42 and the open end 41 b that have rubbed againsteach other, the contaminants are forced out of the contact locationtogether with the lubricant when fitting the lid 42 to the open end 41b. For this reason, the contaminants that are produced when fitting thelid 42 to the open end 41 b are unlikely to enter the enclosing space 41a of the case main body 41. Thus, the manufacturing method disclosedherein reduces the friction between the lid 42 and the open end 41 bwhen assembling the lid 42 to the open end 41 b, and accordingly reducesthe formation of contaminants.

With the manufacturing method disclosed herein, microscopic contaminantsdo not easily form even when the lid and the open end rub against eachother, and even when such contaminants form, they do not easily enterthe enclosing space 41 a of the case main body 41. For this reason, themanufacturing method disclosed herein is suitable when the case mainbody 41 and the lid 42 are made of a material that is prone to formationof contaminants when rubbed. The manufacturing method disclosed hereinis suitable, for example, when aluminum or an aluminum alloy is for thecase main body 41 and the lid 42.

Here, in the step of applying a lubricant, the lubricant may be appliedto at least one of the case main body 41 and the lid 42. For example, inthe embodiment described above, the contact location includes the sidewall 41 b 2 and the stepped portion 41 b 1 of the open end 41 b of thecase main body 41, and the peripheral edge portion 42 a of the lid 42.Accordingly, the lubricant may be applied to either one of the innerside wall 41 b 2 of the open end 41 b of the case main body 41 or theperipheral edge portion 42 a of the lid 42. Alternatively, the lubricantmay be applied to both the inner side wall 41 b 2 of the open end 41 bof the case main body 41 and the peripheral edge portion 42 a of the lid42.

In the above-described embodiment, the open end 41 b of the case mainbody 41 is in a substantially rectangular shape, and includes thestepped portion 41 b 1 along the inner side wall 41 b 2 of the case mainbody 41. The lid 42 is a substantially rectangular-shaped plate materialfitted to the open end 41 b. Herein, the lid 42 is a plate material in asubstantially rectangular shape that corresponds to the shape of theopen end 41 b of the case main body 41, and the lid 42 is shaped so asto substantially precisely fit to the open end 41 b of the case mainbody 41. Furthermore, the lid 42 may in some cases be pressed lightlyinto the open end 41 b when assembled to the open end 41 b.

In that case, the regions surrounding the corner portions 41 c of thesubstantially rectangular-shaped open end 41 b, including the exactcorner portions 41 c, have particularly high rigidity. Accordingly, theregions surrounding the corner portions 41 c are prone to rubbing withthe regions surrounding corner portions 42 c of the lid 42, includingthe exact corner portions 42 c, when the lid 42 is assembled to the openend 41 b. For this reason, in the step of applying a lubricant, thelubricant may be applied to at least one of the corner portions 41 c ofthe substantially rectangular-shaped open end 41 b and the cornerportions 42 c of the lid 42. Herein, the corner portions 41 c of theopen end 41 b may include the regions surrounding the corner portions 41c of the open end 41 b in a substantially rectangular shape. The cornerportions 42 c of the lid 42 may include regions surrounding the exactcorner portions 42 c. That is, the location to which the lubricantshould be applied may be either one of the corner portions 41 c of theopen end 41 b and the regions surrounding the corner portions 41 c, andthe corner portions 42 c of the lid 42 and the regions surrounding thecorner portions 42 c. Alternatively, the location to which the lubricantshould be applied may be both of the corner portions 41 c of the openend 41 b and the regions surrounding the corner portions 41 c and thecorner portions 42 c of the lid 42 and the regions surrounding thecorner portions 42 c.

Herein, for example, the regions surrounding the corner portions 41 c ofthe open end 41 b and the regions surrounding the corner portions 42 cof the lid 42 may be determined to extend at least 20 mm or greateralong the longer sides from the respective shorter sides, and theregions surrounding the corner portions 41 c and 42 c may be determinedto extend at least 1 mm or greater along the shorter sides from therespective longer sides.

Also, when the lubricant is applied to the lid 42, the lubricant may beapplied to a height of 1 mm or higher from the end from which the lid 42is inserted into the case main body 41.

The regions surrounding the corner portions 41 c and 42 c are notlimited to the areas exemplified here. The regions surrounding thecorner portions 41 c and 42 c may be set to the portions surrounding thecorner portions 41 c and 42 c in which the lid 42 and the open end 41 bof the case main body 41 are prone to rubbing against each other.

In addition, the lubricant may be applied to portions where the lid 42and the open end 41 b of the case main body 41 are prone to rub againsteach other, other than the surrounding regions of the corner portions 41c and 42 c.

The application of the lubricant may be operated by a robot arm of anautomatic assembly robot so that an appropriate amount of lubricant isapplied to a predetermined appropriate position on the lid 42 or on theopen end 41 b of the case main body 41. When this is the case, it ispossible that the lubricant may be enclosed, for example, in a cylinderand be supplied in an appropriate amount. Alternatively, the lubricantmay be sprayed through nozzles, for example, in an appropriate amount.The application amount of the lubricant may be adjusted, depending onthe type of the lubricant and the location to which the lubricant is tobe applied, to such a level that the friction between the lid 42 and theopen end 41 b of the case main body 41 can be reduced and also thelubricant can be volatilized at appropriate timing so as not to remainon the battery case in the later processing steps. The applicationamount of the lubricant may be adjusted to such an amount that excessivelubricant can be forced out of the case main body 41 when the lid 42 isassembled to the open end 41 b, from the viewpoint that the contaminantsthat are produced when the lid 42 is assembled to the open end 41 b ofthe case main body 41 need to be ejected.

This embodiment illustrates an example in which each of the open end 41b and the lid 42 is in a flat rectangular shape. However, the shape ofthe lid 42 and the shape of the open end 41 b of the case main body 41are not limited to such a shape. For example, the lid 42 and the openend 41 b of the case main body 41 may be in a circular shape or in anelliptic shape. When this is the case, it is possible that in the stepof applying a lubricant, the lubricant may be applied to the entirecircumference of the peripheral edge portion of the lid 42 and the openend 41 b of the case main body 41. In addition, when it is possible tospecify locations that are particularly prone to rubbing against eachother in the peripheral edge portion of the lid 42 and the open end 41 bof the case main body 41 because of the shape or the assembling method,the lubricant may be applied to the locations that are particularlyprone to rubbing against each other in the peripheral edge portion ofthe lid 42 and the open end 41 b of the case main body 41.

When the lid 42 and the open end 41 b of the case main body 41 are, forexample, in a substantially polygonal shape, the open end 41 b of thecase main body 41 includes a plurality of linear portions and aplurality of curved portions along the edge of the open end 41 b. Inthis case, the contact location also includes a plurality of linearportions and a plurality of curved portions along the edge of the openend. When this is the case, it is possible that in the step of applyinga lubricant, the lubricant may be applied to at least the plurality ofcurved portions of the contact location. Because the curved portionshave higher rigidity than the linear portions, the curved portions areprone to rubbing against each other. When they rub against each other,scratches are likely to form. For this reason, the lubricant may beapplied at least to the curved portions of the contact location.

Thus, the shape of the open end 41 b of the case main body 41 and theshape of the lid 42 are not limited to a substantially rectangularshape, unless specifically stated otherwise. When the open end 41 b ofthe case main body 41 and the lid 42 are in a substantially rectangularshape as described above, the corner portions 41 c and 42 c correspondto the curved portions. The longer sides and the shorter sidescorrespond to the linear portions.

This embodiment illustrates an example in which the lid 42 is fitted toan inner side of the open end 41 b of the case main body 41. However,such an embodiment is merely illustrative. For example, as shown in JP2015-60831 A, the lid may include a portion covering the open end of thecase main body and a wall portion rising from the periphery of thecovering portion. When this is the case, the lid is placed over the openend of the case main body so as to cover the open end of the case mainbody, and the outer side face of the open end of the case main body isbrought into contact with the inner side face of the wall portion of thelid. Then, the outer side face of the open end of the case main body andthe inner side face of the wall portion of the lid are laser welded toeach other. In this case as well, friction between the case main bodyand the lid that are assembled to each other can be reduced by applyinga lubricant to at least a portion of the contact location at which thecase main body and the lid are in contact with each other and assemblingthe lid to the open end with the lubricant having been applied to thecontact location. The lubricant may be a solvent used in a non-aqueouselectrolyte solution for non-aqueous secondary batteries.

As has been described thus far, the method of manufacturing anon-aqueous secondary battery disclosed herein may be applied to a widevariety of non-aqueous secondary batteries in which a lid is fitted toan open end of a case main body. In the variety of non-aqueous secondarybatteries in which a lid is fitted to an open end of a case main body,the method of manufacturing a non-aqueous secondary battery disclosedherein may be applied regardless of the shape of the open end of thecase main body, the shape of the lid, and the assembling structure.

Various embodiments of the method of manufacturing a non-aqueoussecondary battery have been described hereinabove according to thepresent disclosure. Unless specifically stated otherwise, theembodiments of the method of manufacturing a non-aqueous secondarybattery described herein do not limit the scope of the presentinvention.

What is claimed is:
 1. A method of manufacturing a non-aqueous secondarybattery, comprising the steps of: preparing a case main body, the casemain body including an enclosing space for enclosing an electrodeassembly and an open end for inserting the electrode assembly into theenclosing space; preparing a lid to be fitted to the open end; applyinga lubricant to at least a portion of contact locations at which the casemain body and the lid are in contact with each other; and assembling thelid to the open end with the lubricant having been applied to thecontact locations, wherein the lubricant is a solvent used in anon-aqueous electrolyte solution for non-aqueous secondary batteries. 2.The method according to claim 1, wherein, in the step of applying alubricant, the lubricant is applied to at least one of the case mainbody and the lid.
 3. The method according to claim 1, wherein: the openend of the case main body includes a plurality of linear portions and aplurality of curved portions arranged along an edge of the open end, andeach of the contact locations includes a plurality of linear portionsand a plurality of curved portions arranged along the edge of the openend; and in the step of applying a lubricant, the lubricant is appliedto at least the plurality of curved portions of the contact locations.4. The method according to claim 1, wherein: the open end of the casemain body is in a substantially rectangular shape and includes a stepalong an inner side wall of the case main body; the lid is asubstantially rectangular-shaped plate material fitted to the open end;and in the step of applying a lubricant, the lubricant is applied to atleast one of corner portions of the substantially rectangular-shapedopen end and corner portions of the lid.
 5. The method according toclaim 1, wherein the lubricant comprises at least one solvent selectedfrom the group consisting of cyclic carbonate solvents, chain carbonatesolvents, and ether solvents.
 6. The method according to claim 1,wherein the lubricant comprises at least one solvent selected from thegroup consisting of ethyl methyl carbonate, ethylene carbonate, dimethylether, diethyl carbonate, propylene carbonate, and dimethyl carbonate.